Saori Kurosawa

Differential Effects of Propofol and Sevoflurane on Heart Rate Variability

Background Propofol is reported to reduce both sympathetic and parasympathetic tone; however, it is not clear whether the changes in heart rate variability are associated with depth of anesthesia. The purposes of the present study were (1) to evaluate the changes in heart rate variability at different depths of hypnosis and (2) to compare the effects of propofol on heart rate variability with that of sevoflurane. Methods Thirty patients were randomly allocated into the propofol or sevoflurane for induction of anesthesia. The depth of hypnosis was monitored by the Bispectral Index (BIS). Spectral analysis of heart rate variability using a maximum-entropy method resulted in a characteristic power spectrum with two main regions, a high frequency (HF) and a low frequency (LF). Hemodynamics, entropy, LF, HF, and LF/HF were monitored when the patients were awake and after induction of anesthesia. Results Both propofol and sevoflurane decreased blood pressure in a BIS-dependent manner, whereas heart rate showed no significant changes during the study period. In the propofol group, entropy and HF decreased with a reduction in the BIS value. Although LF decreased after induction of anesthesia, propofol caused no further decrease in LF in spite of a reduction in the BIS value. In the sevoflurane group, LF decreased with a reduction in the BIS value. Entropy and HF decreased after induction of anesthesia (BIS at 80); however, no further decreases were observed in spite of a reduction in the BIS value. Conclusions Induction of anesthesia with propofol decreased blood pressure, entropy, and HF in a BIS-dependent manner, indicating that propofol reduces cardiac parasympathetic tone depending on the depth of hypnosis. Conversely, sevoflurane did not show the BIS-dependent decreases in heart rate, blood pressure, HF, and entropy, indicating that sevoflurane has little or no effect on cardiac parasympathetic tone.

A comparison of the failure times of pulse oximeters during blood pressure cuff-induced hypoperfusion in volunteers.

Important information may not be obtained if the pulse oximetry signal is lost during inflation of a cuff for blood pressure measurement, particularly in patients with hemodynamic instability. In the present study, we compared the failure times of pulse oximeters during cuff-induced hypoperfusion in volunteers. A pulse oximeter sensor was attached to the index finger, and a blood pressure cuff was attached to the same arm of each volunteer. MasimoSET Radical (Masimo), Nellcor N-395 (N-395), Nellcor N-20PA, and Nellcor D-25 were tested. To evaluate the failure time of each pulse oximeter, time to peak of cuff pressure, time to loss of signal, time to recovery of signal, and failure interval were measured. All measurements were performed three times for each pulse oximeter and were averaged. There were no differences in hemodynamic measurements among the groups. Time to loss of signal was longer in Masimo than the other pulse oximeters. Masimo and N-395 showed significantly shorter times to recovery of signal than those of the other two pulse oximeters. Failure interval was in the order of Masimo ≪ N-395 < Nellcor D-25 = Nellcor N-20PA. Masimo did not lose a signal as rapidly as the other oximeters studied. Masimo was similar in performance to the N-395 at providing useful data sooner than conventional technology after a loss of the signal. These observations suggest that data will be more available with fewer false-positive alarms when using the Masimo oximeter followed by the N-395 when compared with conventional oximeters.

Landiolol, esmolol and propranolol protect from ischemia/reperfusion injury in isolated guinea pig hearts

PurposeBeta blockers are thought to exert beneficial effects on the ischémic heart. The authors examined the effects of landiolol (ONO 1101), a highly selective βl antagonist, propranolol, a nonspecific β blocker, and esmolol, a selective β l antagonist, on postischemic contractile recovery. Drugs were given prophylactically.MethodsIschemia-reperfusion in isolated guinea pig hearts was induced by stopping the perfusion for 45 min and reperfusing for 60 min. Hearts (n = 7 in each group) were treated with or without propranolol (1 or 10μM), esmolol (5 or 50μM), or landiolol (20, 100 or 500 μM) ten minutes before inducing ischemia.ResultsAt the end of reperfusion, left ventricular pressure (LVP) recovered to 64 ± 3% of the baseline value in the control group. With 1 and 10 μM propranolol, LVP recovered to 90 ± 5% and 100 ± 6% of the baseline value at 60 min after reperfusion, respectively. FiftyμM but not 5μM of esmolol resulted in restoration of LVP to 97 ± 17% of the pre-ischemic value at 60 min after reperfusion. In hearts pretreated with 100 and 500 μM landiolol, LVP was restored to 109 ± 5% and 104 ± 596 of the baseline value, respectively. Landiolol 100μM did not depress LVP in the pre-ischemic period.ConclusionsThe present study shows that landiolol, an ultrashort-acting cardioselective β l blocker, has cardioprotective effects on ischemia-reperfusion injury in isolated guinea pig hearts. All three β blockers were equally protective but the intermediate dosage of landiolol preserved LVP during the pre-ischemic period.RésuméObjectifOn croit que les bêtabloquants ont des effets bénéfiques sur le cœur ischémique. Les auteurs ont vérifié les effets du iandioioi (ONO 1101), un antagoniste βl hautement sélectif, du propranolol, un β bloquant non spécifique, et de l’esmolol, un antagoniste β l sélectif, sur la récupération contractile postischémique. Les médicaments ont été administrés préventivement.MéthodeLischémie-reperfusion a été induite dans des cœurs de cobaye isolés en stoppant la perfusion pendant 45 min et en reperfusant pendant 60 min. Les cœurs (n = 7 dans chaque groupe) ont été traités avec ou sans propranolol (1 ou 10 μM), esmolol (5 ou 50 μM) ou landiolol (20, 100 ou 500 μM) dix minutes avant l’induction de l’ischémie.Résultats:ÀLa fin de la reperfusion, la pression ventriculaire gauche (PVG) avait retrouvé 64 ± 3 % de sa valeur de base dans le groupe témoin. Avec I et 10 μM de propranolol, la PVG a été récupérée respectivement à 90 ± 5 % et 100 ± 6 %, 60 min après la reperfusion. La dose de 50 μM, non celle de 5 μM, d’esmolol a été suivie de la restauration de la PVG à 91 ± 17% de la valeur préischémique, 60 min après la reperfusion. Dans les cœurs prétraités avec 100 et 500 μM de landiolol, la PVG a été restaurée à 109 ± 5 % et à 104 ± 5 % de sa valeur de base, respectivement. La dose de 100 μM de landiolol n’a pas causé de baisse de la PVG en période préischémique.ConclusionLa présente étude montre que le landiolol, un β l bloquant cardiosélectif à action très brève, a des effets cardioprotecteurs sur les lésions résultant de l’ischémie-reperfusion dans des cœurs de cobaye isolés. Les trois β bloquants ont été également protecteurs, mais la dose intermédiaire de landiolol a diminué la PVG pendant la période préischémique.

Effects of thiopental on bispectral index and heart rate variability.

Background and objective: Thiopental has been reported to reduce sympathetic tone, however, it is not clear whether change in heart rate variability is associated with depth of anaesthesia. The purpose of the present study was to evaluate changes in heart rate variability at different depths of hypnosis during induction of anaesthesia with thiopental. Methods: We studied 17 ASA I patients scheduled for minor surgery. The depth of hypnosis was monitored by the BIS. Spectral analysis of heart rate variability using a maximum entropy method resulted in a characteristic power spectrum with two main regions, a high frequency and a low frequency. Haemodynamics, entropy, low frequency, high frequency and low frequency/high frequency were monitored in an awake state and after the induction of anaesthesia. Results: Heart rate increased in a BIS‐dependent manner, whereas blood pressure showed no significant changes during the study period. High frequency, entropy and low frequency decreased with a reduction in the BIS value. Low frequency/high frequency showed no significant change during the study period. Conclusions: Induction of anaesthesia with thiopental increased heart rate and decreased high frequency, entropy and low frequency in a BIS‐dependent manner, indicating that thiopental reduces cardiac parasympathetic tone depending on the depth of hypnosis.

A simple way to prevent infection from removed laryngeal mask airways

To the editor: It is important that all anesthesiologists pay attention to reducing the risk of exposure to blood-borne hazards. Recently, occult blood contamination was reported to occur in 76% of laryngeal mask airways (LMAs), while visible blood contamination occurred in 12% [1]. The presence of various secretions also increases the risk of contamination. We have devised a simple means to protect the operating room from bloodand/or secretion-mediated Letters to the editor